types: clear remaining tsc errors across 41 files (76→14, behavior-preserving)

Per-file type-only fixes surfaced after the Supabase client was correctly
typed. All fixes preserve runtime behavior; no any/ts-ignore/ts-expect-error.

- lib/supabase/client.ts: annotate the browser client as SupabaseClient<Database>
  (same ssr/js drift as server.ts; fixes it centrally for all callers).
- Supabase embedded-select joins whose FK metadata is missing from the
  generated types are bridged with `as unknown as <target>` + a TODO to remove
  after regenerating types/database.ts.
- setState optimistic-update variance and raw <select> enum values cast to the
  precise element/union type; .insert payload fields (Json, enums) given the
  precise column type via satisfies/field casts.
- Added narrowing guards where a value was legitimately nullable (comms channel,
  public form page) without changing the intended path.

The 14 remaining errors are confined to the four files fixed in Phase B (real
bugs + the tautological actions.test rewrite). 639 tests still green.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

app/(app)/ops/new/page.tsx

@@ -1,4 +1,5 @@
 import { createClient } from '@/lib/supabase/server'
+import type { Tables } from '@/types/database'
 import KbEntryEditor from '../[id]/kb-entry-editor'
 
 export default async function NewOpsEntryPage() {
@@ -10,5 +11,5 @@ export default async function NewOpsEntryPage() {
     .from('space_members').select('space_id, role, display_name').eq('user_id', user.id).in('status', ['current', 'unverified', 'late']).single()
   if (!member) return null
 
-  return <KbEntryEditor member={member} />
+  return <KbEntryEditor member={member as Tables<'space_members'>} />
 }